Insects and diseases can pose serious threats to a forest’s health. Our foresters monitor insect and disease activity and trends, and respond to emerging threats to our communities’ forests.

Common Insect & Disease Concerns

As soon as you notice any abnormality in your tree’s appearance, you must begin careful analysis to gain an understanding of the problem. By examining the specific symptoms of damage and understanding their causes, you can make a reasonable diagnosis of the problem and select the proper treatment using this guide to Diagnosing Tree Disorders.

If your questions cannot be resolved with the information provided in the guide or the links below, please contact the Franktown District office at (303) 660-9625.

Foresters are available to conduct site visits to look at specific insect or disease concerns on your property. These visits are by appointment only, and have an associated service fee. To schedule an appointment please call the Franktown District office.

Pine sawfly mature larvae. Photo: W. Ciesla
Pine sawfly mature larvae. Photo: W. Ciesla

Common Local Insects & Diseases

Ponderosa Pine
Douglas-fir
Aspen
Gambel Oak

Other Insects of Concern

Other Damage

There are non-insect and disease-related factors that affect trees and create signs/symptoms that can be confused with insect and disease activities. Below are common disorders/damage that affect conifers on the district:

The 2015 Report on the Health of Colorado’s Forests (3 MB PDF) provides an overview of insect and disease conditions in all of the state’s forests.

Forest Insect & Disease Aerial Survey

The annual survey is led, coordinated and funded by the U.S. Forest Service. A small fixed-wing aircraft is flown between 1,000 to 1,500 feet above the treetops while surveyors mark on a map the location, number and identity of trees affected by insects or diseases. The CSFS has assisted in the aerial survey since the 1970s and began playing a larger role in 1997.

For more information about the state aerial survey, visit U.S. Forest Service Rocky Mountain Region.